There is a general misconception that the initial voltage defined for a utility or a swing bus generator is the initial operating voltage at the connected bus. The initial voltage is actually the internal voltage before the source impedance.

For Load Flow calculation, if the “Include Source Impedance for Utility and Swing Generator” option in the load flow study set up is checked, an internal generator impedance branch is created, one side of this branch is the source bus, the other side is the internal bus of the source, the voltage of this internal source bus will be the constant defined as this initial voltage. If this option is unchecked, the voltage of the source bus will be the constant as this initial voltage.